Colonoscopy for removal of polyps

Colonoscopy and removal of polyps is the most powerful cancer prevention method available in medicine.  Very small polyps can be removed by operating forceps passed through the colonoscope.  Larger polyps (greater than 5 mm) are generally removed with a metal wire called a ‘snare’.  The snare has a loop at the end like a lasso, and this loop is placed around the polyp and tightened.  When it is tightened enough, it will cut through the polyp base, severing the polyp from the bowel wall.  Before the snare cuts through the polyp completely, the colonoscopist sends an electrical current down the snare to cauterize the vessels in the polyp.  This combination of tightening the snare around the polyp and passing electricity down the wire at the same time permits the polyp to be removed while vessels beneath it are simultaneously sealed to prevent bleeding.  The loose polyp is then removed through or with the colonoscope and sent for microscopic assessment.

The two main risks of polypectomy are bleeding and perforation.  Bleeding can occur if a vessel is not cauterized completely at the time that the snare loop is finally tightened.  As one might imagine, there is a bit of an art form in knowing how much cautery to use and when and how quickly to tighten the snare while cauterizing, etc.  Too much cautery will destroy the polyp entirely or will burn through the bowel wall resulting in a perforation.  Too little cautery will leave bleeding vessels.

Every polypectomy is different due to differences in polyp sizes, shapes, amount of tissue electrical resistance, firmness, etc.  So cases of bleeding and perforation can occur even in the most experienced hands.  In addition to perforation caused by cautery current, perforation can also occur if a portion of the bowel wall is caught up on the snare, unbeknownst to the colonoscopist.  An experienced colonoscopist will take great pains to ensure this does not happen, but this is a recognized potential complication.

Once the polyp type has been determined by the pathologist, the Pezim Clinic physician will meet with the patient and discuss the findings.  This usually happens about 3 weeks after the procedure.  Depending on the nature of the polyp(s), a program of a follow-up colonoscopy or specific treatment will be recommended.

© Pezim Clinic, Vancouver, British Columbia, Canada